Oscillators of this general type are known in the art. For example, U.S. Pat. No. 3,810,417 describes a method and an apparatus for adjusting a work piston in a cylinder. The work piston is made to vibrate by means of introducing and removing a pressure medium, and a control unit is located between the work cylinder and a reservoir for the pressure medium. There is a control cylinder in this control unit which has a control piston provided with axial grooves. The control piston is driven such that it is both axially displaceable and rotatable, so that a controlled quantity of the pressure medium can be sent in the desired direction at a given time. An apparatus of this kind, if it has a piston which is prestressed at one end, requires three lines for the pressure medium between the reservoir and the work cylinder, while with a cylinder that moves in both directions four lines are required. These lines must be sealed appropriately, and furthermore they cause not only a loss in power but a delay in the effect exerted on the work cylinder, so that the oscillation frequency can be increased up to an order of magnitude of 100 Hz.
In Swiss application No. 526,724, an apparatus for generating pneumatic rectangular oscillations is described, thus providing a further possible embodiment for a control unit such as may be used with the foregoing apparatus.
A fluidics oscillator is described in U.S. Pat. No. 4,007,625 which includes an oscillator crystal for the purpose of closing off one output of the oscillator. This oscillator crystal serves to pick up the oscillator frequency when determining the mixture ratio of a gas mixture.